title: Rust disease of eucalypts, caused by Puccinia psidii, did not originate via host jump from guava in Brazil.
abstract: The rust fungus, Puccinia psidii, is a devastating pathogen of introduced eucalypts (Eucalyptus spp.) in Brazil where it was first observed in 1912. This pathogen is hypothesized to be endemic to South and Central America and to have first infected eucalypts via a host jump from native guava (Psidium guajava). Ten microsatellite markers were used to genotype 148 P. psidii samples from eucalypts and guava plus five additional myrtaceous hosts across a wide geographic range of south-eastern Brazil and Uruguay. Principal coordinates analysis, a Bayesian clustering analysis and a minimum-spanning network revealed two major genetic clusters among the sampled isolates, one associated with guava and another associated with eucalypts and three additional hosts. Multilocus genotypes infecting guava differed by multiple mutational steps at eight loci compared with those infecting eucalypts. Approximate Bayesian computation revealed that evolutionary scenarios involving a coalescence event between guava- and eucalypt-associated pathogen populations within the past 1000 years are highly unlikely. None of the analyses supported the hypothesis that eucalypt-infecting P. psidii in Brazil originated via host jump from guava following the introduction of eucalypts to Brazil approximately 185 years ago. The existence of host-associated biotypes of P. psidii in Brazil indicates that this diversity must be considered when assessing the invasive threat posed by this pathogen to myrtaceous hosts worldwide.
authors.affiliation: Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.
authors.forename: Rodrigo N
authors.initials: RN
authors.lastname: Graça
authors.forename: Amy L
authors.initials: AL
authors.lastname: Ross-Davis
authors.forename: Ned B
authors.initials: NB
authors.lastname: Klopfenstein
authors.forename: Mee-Sook
authors.initials: MS
authors.lastname: Kim
authors.forename: Tobin L
authors.initials: TL
authors.lastname: Peever
authors.forename: Phil G
authors.initials: PG
authors.lastname: Cannon
authors.forename: Cristina P
authors.initials: CP
authors.lastname: Aun
authors.forename: Eduardo S G
authors.initials: ES
authors.lastname: Mizubuti
authors.forename: Acelino C
authors.initials: AC
authors.lastname: Alfenas
mesh_terms: D001487:Basidiomycota / Q000145:classification* / Q000235:genetics; D001499:Bayes Theorem; D005075:Biological Evolution; D001938:Brazil; D005052:Eucalyptus / Q000382:microbiology*; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D058507:Host Specificity; D018895:Microsatellite Repeats; D008957:Models, Genetic; D058885:Multilocus Sequence Typing; D016533:Mycological Typing Techniques; D010935:Plant Diseases / Q000382:microbiology*; D025341:Principal Component Analysis; D031647:Psidium / Q000382:microbiology*; D014583:Uruguay
keywords: emerging disease; host jump; microsatellite; pathogen diversity; population structure